The invention relates to a method for forming thin-walled products from plastic in a mold.
Thin-walled products are usually manufactured from plastic by injection molding in a mold. To this end, materials are used having a relatively high Melt Flow Index (MFI), at least a high melt. Such a high MFI means that the plastic in flowable form has a low viscosity and hence can traverse relatively long flow paths of small dimensions in a mold cavity. The ratio between the length of a flow path and the minimum passage height of the flow path involved is usually designated as the Melt Flow Rate (MFR). A high MFR therefrom means a relatively long, narrow flow path. Injection molding is possible, in principle, with plastics having a high MFI, with a direct relation existing between the MFI and the MFR. A higher MFR required a higher MFI. It will be clear, therefore, that plastics having a low melt, at least a low MFI, do not permit of injection molding, at least not to form thin-walled plastic products, since thin-walled plastic products have an MFR that is too high for that. This means that only products having relatively thick walls and relatively short flow paths can be injection molded from low-melt plastics. Moreover, such methods require relatively high closing forces and a relatively long cycle time, which is economically disadvantageous.
One object of the invention is to provide a new method for forming plastic products in a mold.
Another object of the invention is to provide such a method with which products can be formed in a mold from plastics having a relatively low melt.
A further object of the invention is to provide a method with which products can be manufactured in a mold, from plastic, in which a relatively low closing force can be used and a method with which relatively short cycle times can be achieved.
These and further objects are achieved with a method according to the invention.